The present invention relates generally to plant tissue culture and methods for genetically altering cells of higher plants. More particularly, the present invention relates to methods for genetically transforming banana plants (genus Musa), and obtaining regenerated plants therefrom.
Banana, including dessert bananas, plantain and cooking bananas, is among the most important staple food crop in the developing world. In fact, the fruits are the staple food for approximately 400 million people. The production of bananas has recently been seriously threatened by pests and many fungal, bacterial and virus diseases. Traditional methods of genetic improvement, however, cannot be used easily to transfer missing resistance characteristics to bananas, given sterility and ploidy issues arising in the triploid species.
Since breeding for improved traits is difficult and time consuming in banana plants, a preferred method for creating new varieties of banana is genetic engineering. In fact, genetic improvement of banana plants is a key goal of the scientific community. Genetic engineering of banana plants involves, among other methodologies, techniques for the introduction of exogenous DNA into banana cells and the regeneration of said transformed cells into banana plants identical to the original plant except for the presence of the introduced DNA. These techniques for gene introduction are preferably efficient in all steps of the process, from DNA delivery into the plant cells to regeneration of intact plants from the transformed plant cells.
Techniques for the in vitro culture of banana plants, including methods for the regeneration of plants from banana tissue cultures, have been described previously. In fact, there are commercial banana micropropagation facilities in which banana tissue culture is routinely practiced. However, these standard micropropagation methods are not suitable as the basis for a gene introduction method because in general, they not are compatible with DNA delivery.
In general, plants can be regenerated from tissue culture by direct organogenesis, indirect organogenesis, or somatic embryogenesis. Methods have been described previously for regenerating banana plants via direct organogenesis and somatic embryogenesis.
One method reported for banana transformation involves direct organogenesis and the use of an Agrobacterium-mediated DNA delivery. Arntzen, Biotechnology (1995); WO 95/15678. Another method for banana transformation that has been described involves somatic embryogenesis and a biollistic DNA delivery. Sagi (1995). It is, however, particularly desirable to find new and efficient methods for producing transgenic Musa plants.